Bagging of agricultural materials such as silage is accomplished by large mobile machines having a wheeled chassis supporting a tunnel. The tunnel is irregularly shaped but roughly resembles a short cylinder about 4 ft. in length and 6 ft.-12 ft. in diameter. Material is forced into the tunnel through an inlet end at the forward end of the tunnel, the material is compacted in the tunnel and then fed through the open end at the rear of the tunnel and into a bag that encloses and surrounds the open rear end of the tunnel. The feeding process is continuous and the bag is deployed off the tunnel as the machine moves away from the bag. When filled, the bag may be 8 ft.-12 ft. in diameter and up to 500 ft. in length.
A concern in the bagging of such materials is compaction and total filling of the bag (sometimes referred to simply as compaction). If the material does not fill the bag, i.e., it is not tightly compacted into the bag, there is the obvious loss of efficiency (more bags are required for storing a given quantity of material, the bags take up more space, filling bags too loosely takes more time than filling one bag tightly) and the not so obvious concern for bag tearing (loose folds in the bag are more likely to be snagged and wind damaged) and material preservation (the compacted material inhibits circulation of air which induces spoiling of the material).
The early versions of these bagging machines attained the desired fill and compaction by placing a backstop at the end of the bag with cables extended from the backstop along the sides of the bag and to a reel at each side of the bagging machine. The reels deployed cable only when a desired back pressure was achieved and thus as the bag was filled, additional bag length was deployed only when the existing bag length was desirably compacted.
The backstop and cable (each cable being, e.g., 300 ft. in length) were initially considered an undesirable necessity. Once the bag was filled, the long cables had to be rewound back onto the reels, the backstop loaded onto the machine and hauled to a new site where start up required remounting the backstop and cable connections.
Compaction can be enhanced by providing the bagging machine with brakes. However, the pressures needed to achieve sufficient compaction and filling of the bag will typically produce skidding of the machine's wheels and particularly in conditions where the ground surface is slippery as when wet. Other systems intended to replace the backstop and cable connection include devices in the tunnel, e.g., internal cables and gate-like members that impede the flow through the tunnel (see U.S. Pat. Nos. 5,676,594, 5,857,313 and 5,860,271). Still others provide for an anchor device to be embedded in the bag material (see U.S. Pat. No. 5,899,247 and application for U.S. patent Ser. No. 09/335,240). However, none of these replacement systems achieve the desired compaction as previously achieved using the backstop and cable system. The present invention is believed to be a step closer to achieving the desired compaction and filling of the bag.